Ambulance Service medical director Dr Nigel Ruddell said preliminary investigations showed there was a crush towards the front door of the hotel, which led to people falling.

Security camera footage is being examined and police have appealed for videos taken by those present.

PSNI Assistant Chief Constable Alan Todd said it would be an "extensive investigation with potentially hundreds of witnesses, many of whom are teenagers", adding that the probe would "rightly be painstaking and detailed".

He urged young people who were at the hotel to contact them.

"We are investigating the deaths of three young people, young people just like you. That is our focus. We want to be able to give their families answers and your recollection of the events as they unfolded is crucial."

Catholic Primate Eamon Martin said last night that "our heartfelt thoughts and prayers are with the families and friends of Lauren, Connor and Morgan, and with all of those who were caught up in the horror and distress of what happened, including those injured and traumatised, and the emergency services and staff who responded".

Sean McPeake, chairman of Mid Ulster District Council which has responsibility for licensing of entertainment venues, said it was working closely with the emergency services in the aftermath of the tragedy.

Books of condolence for Morgan Barnard, Lauren Bullock & Connor Currie who tragically lost their lives at the Greenvale Hotel, Cookstown are now open at @burnavontheatre, Cookstown, Ranfurly House, Dungannon and the Bridewell Magherafelt. pic.twitter.com/mCsIoPMzEn